1. Field of the Invention
The present invention generally pertains to a wafer carrier designed for supporting, constraining, storing and precisely positioning semi-conductor wafer disks for use in the production of integrated circuits. More specifically, the present invention pertains to a key slot for actuating a latching mechanism to secure a door on a wafer container enclosure.
2. Discussion of the Related Art
Processing of semi-conductor wafers into finished electronic components typically requires many processing steps where the wafers must be handled and processed. The wafers are very valuable, and are extremely delicate and easily damaged by physical and electrical shocks. In addition, successful processing requires the utmost in cleanliness, free of particulates and other contaminants. As a result, specialized containers or carriers have been developed for use during processing, handling and transport of wafers. These containers protect the wafers from physical and electrical hazards, and are sealable to protect the wafers from contaminants.
Various configurations of door enclosures and latching mechanisms for sealable wafer carriers are known in the art. Known latching mechanisms often use rotatable actuating members. These actuating members may include a cam, but sometimes are geared. The actuating member in such a mechanism is generally rotated robotically from outside the carrier using a key having a substantially rectangular cross-section. The key is inserted through an opening in the outer surface of the door and into a key slot formed in the rotatable actuating member. Previously, key slots have generally been rectangular in cross-section.
Tolerance must be provided between the key and the key slot in order to allow for insertion of the key. When the key is rotated to cause rotation of the cam member, this tolerance allows the key to rotate slightly within the key slot. The corners of the key bear against the sides of the key slot and become the points where the rotational force of the key is transmitted to the key slot and associated cam member. A relatively small area of the key is in contact with the sides of the key slot, and since all of the rotational force is transmitted through this small area, very high stress levels are experienced in the key and the key slot sides at the point of contact. The result is abrasion of the materials and the generation of undesirable particulate contaminants.
To minimize the abrasion problem when using a rectangular key slot, the key to key-slot tolerances must be kept relatively small. Reduced tolerance, however, can cause key insertion difficulty and key jams, resulting in key slot and key damage. Such damage causes undesirable particulates, along with process inefficiencies and production disruption.
What is needed is some sort of key slot for use with a rectangular cross-section key that offers increased bearing surface while also allowing a relatively large key to key-slot tolerance.
The present invention fulfills the described needs by providing a greater bearing area where the key is in contact with the key slot, and by also allowing for increased tolerance between the two parts. In the invention, the key slot is made in a generally hourglass shape. The hourglass shape allows the flats of the key to bear against the key slot sides rather than the corners of the key, allowing a larger area for force transmission and correspondingly reduced material stress.
The interior surfaces of the key slot may be formed from hard, abrasion resistant material such as polyether imide (PEI) plastic, reducing abrasion of material and particulate generation. The key slot material may be electrically conductive to allow for an electrical path to ground. Since rotation of the key within the key slot need not be as closely restricted, a larger key slot with greater key to key slot tolerances can be used, resulting in relatively easier key insertion, less component damage and less key jamming.
Accordingly, it is an object and advantage of the invention to reduce generation of particulate matter resulting from contact between a key and a key slot in a wafer carrier latch mechanism.
It is a further object and advantage of the invention to reduce key jamming and resultant production inefficiencies.
It is a still further object and advantage of the invention to reduce key and key slot damage resulting from insertion and removal of the key.
Additional objects, advantages, and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.